1. Field of the Invention
The present invention relates to a stable crystal form of the methane sulfonic acid addition salt of 4-(4-methyl piperazin-1-yl methyl)-N-[4-methyl-3-(4-pyridin-3-yl)-pyrimidin-2-yl amino) phenyl]-benzamide of Formula I, and to a process for the preparation thereof. The crystal form according to the invention may be used in the preparation of pharmaceutical formulations for use in tumor therapy.
2. Description of Related Art
Imatinib is the international non-proprietary name of 4-(4-methyl piperazin-1-yl methyl)-N-[4-methyl-3-(4-pyridin-3-yl)-pyrimidin-2-yl amino) phenyl]-benzamide. Imatinib is currently used for the treatment of patients with certain types of leukaemia (most commonly chronic myeloid leukaemia) and a rare type of cancer known as gastro-intestinal stromal tumour (GIST). The structural formula of imatinib is given below.

EP564409 and U.S. Pat. No. 5,521,184 first reported a process for preparation of 4-(4-methyl piperazin-1-yl methyl)-N-[4-methyl-3-(4-pyridin-3-yl)-pyrimidin-2-yl amino) phenyl]benzamide of Formula I and the use thereof, especially as an anti-tumor agent. However, it does not specify any crystal modifications.
Patent Application WO 99/03854 disclosed two polymorphic forms of Methane sulfonic acid addition salt of imatinib (Imatinib Mesylate) viz: an (α) Alpha crystal form and a (β) Beta crystal form and the processes for their preparation. The process for the preparation of the alpha crystalline form comprises suspending imatinib base in ethanol, adding methane sulfonic acid dropwise to the said solution, heating the solution to reflux and filtering; evaporating the filtrate to 50%, filtering off the residue; evaporating the mother liquor to dryness; suspending the residue and filtered material in ethanol; dissolving under reflux conditions by simultaneously adding water; cooling overnight, filtering and drying to obtain alpha crystalline form. The obtained alpha-crystalline form is not stable, is highly hygroscopic, is amorphous in nature and not useful for the preparation of pharmaceutical preparations.
The previously known method for producing the alpha-crystal form of methane sulfonic acid addition salt of the compound of Formula I involves the precipitation of the salt from its solution in non-alcoholic solvents. It has also been acknowledged in the prior art that the α-crystal form obtained by such a process was inconsistent and hence had an undesirable property such as hygroscopic nature and unfavourable flow characteristics. It was thus an unstable crystal form and unsuited for pharmaceutical preparations.
The known process for preparing the beta-crystal form involves use of an alcoholic solvent such as methanol or ethanol, or a mixture of acetone and water or dimethyl formamide and crystallization is induced by seeding.